Various exhaust gas purification systems for purifying nitrogen oxides in an exhaust gas discharged from an internal combustion engine, such as the engine of an automobile, have been developed. Patent Document 1 indicated below, for example, describes an exhaust gas purification system for purifying an exhaust gas of an internal combustion engine, the exhaust gas purification system having a selective catalytic reduction catalyst and a NOx occluding reduction type catalyst provided in series sequentially from an upstream side toward a downstream side in an exhaust gas flow-through direction of an exhaust passage of the internal combustion engine, and also having a reducing agent adding device provided upstream of the selective catalytic reduction catalyst.    Patent Document 1: JP-A-2004-218475